Base stations for communications systems are known. Because the base station is so central to proper performance of the systems, carriers or system operators or providers of communication services have demanded that these base stations demonstrate a high level of availability. Thus many of the critical features or functions within these stations, such as central processors or switches and timing references or clocks are often redundant. Base stations having redundant capabilities such as a central clock or reference usually include the ability to switch over to the redundant clock or function.
In complex base stations having a multiplicity of communication resources or cards, such as radio frequency transceiver cards and base band processing cards, some or all repeated for each radio channel that is part of the base station, distribution of a redundant clock and particularly switching from one to another clock has proven to be a significant technical problem especially where the respective cards need to maintain synchronization or phase alignment.
In addition, the present marketplace demands base stations that are suited to handle different types of systems, for example, analog and CDMA spread spectrum systems or generally legacy systems and presently being deployed systems. It is often difficult to design communication cards or resources that efficiently operate off a single clock signal for the different systems.
What is needed is a method and apparatus for a redundant clock that addresses concerns such as these and others that will become more evident from the discussions below.